One consequence of augmentative bio-
logical control’s initial success in citrus was
its subsequent development and spread to
other citrus pests and their natural enemies
and to other commodities in a variety of
locations and contexts (e.g. Flanders, 1930,
1942; Voegelé et al., 1975; Stinner, 1976;
Hassan, 1981; Ables and Ridgway, 1981;
Ridgway and Vinson, 1976; King et al., 1985;
Bigler, 1986; van Lenteren and Woets, 1988;
Ridgway et al., 1998). Pesticide resistance
and the environmental impacts of pesti-
cides, along with increasing public concern
and growing regulations against pesticide
use, have been major factors stimulating the
development of alternative pest-control tac-
tics. Augmentative biological control has
been an important alternative pest-suppres-
sion tactic.
Augmentative biological control consists
of three elements: (i) the mass production of
an augmentative biological control agent(s)
and its economics; (ii) the agent’s release
and impact on a target’s population density
in the field – that is, the mechanics of
release, along with the ecology and popula-
tion dynamics of the agent and its host or
prey; and (iii) the suppression of a pest
complex as part of a sustainable pest-man-
agement programme at a specific geograph-
ical location, while producing a crop
economically.
Fundamental to an augmentative biolog-
ical control programme is the development
of a means of producing the natural enemy
inexpensively and in large numbers, while
maintaining their quality at a level for them
to be effective. Traditionally, this entails
developing a means of producing: (i) the
host plant or plant product; (ii) the host
insect; and (iii) the natural enemy or ene-
mies (Flanders, 1949; Fisher, 1963).
Historically, the development of a produc-
tion system has involved serendipity, prac-
tical experience and tenacity, coupled with a
great deal of ‘art’ or ‘intuition’ gained from
practical experience, along with experimen-
tation to verify the hunches and intuition
that have been gained from observation and
experience (e.g. Flanders, 1930, 1949; Finney
and Fisher, 1964).
Economics of citrus pest managementThat an integrated pest management (IPM)
approach involving augmentative biological
control has practical value to the manage-
ment of California’s citrus pests can be seen
in the response by a group of citrus growers
who formed the Fillmore Citrus Protective
District in 1922 (Graebner et al., 1984). This
district was organized to spread the cost of
pest management among its grower mem-
bers and thereby reduce each grower’s indi-
vidual pest-management costs while
increasing pest control’s reliability through
the use of natural enemies. Thus, it is the
cost-effectiveness of the whole IPM pro-
gramme that is the important criterion, not
the cost of controlling each individual pest
species or of producing each natural-enemy
species (Graebner et al., 1984). For example,
in the decade between 1971 and 1980, the
average Protective District grower spent
$71.88 ha^1 annually for pest control. This
contrasted with the average pest-control costs
of $362.50 ha^1 for a non-member – that is, an
orange grower in the same Ventura County
location of California but who does not
belong to the district. In the last year of the
decade, 1980, a member grower paid $32.50
ha^1 in assessment fees and spent an addi-
tional $60 ha^1 for the control of various
pests, such as weeds, ants and brown-rot con-
trol (a fruit rot, Phytophthoraspp.) (Weppler,
1998). Thus, the $92.50 expended by a grower
member for pest control during the last year
of the decade was still substantially less than
the decade average ($362.50 ha^1 ) paid by the
average, non-member grower during the
entire decade. This was the case even though
producing the soft-scale parasitoid,
Metaphycus helvolus(Compere) (Hymenoptera:
Encyrtidae), to control black scale, Saissetia
oleae (Olivier) (Homoptera: Coccidae), is
more expensive than a single pesticide appli-
cation for this pest, as judged by the para-
sitoid’s market price as charged by the
commercial insectaries (Cranshaw et al.,
1996). However, it is the disruptive nature of
these pesticide applications for black- and
California red-scale suppression that causes
the overall increase in pest-management
costs. The application of broad-spectrum pes-234 R.F. Luck and L.D. Forster